The present invention relates to a metal gasket with edge support beads to prevent upward expansion or deformation of a cylinder head of an engine.
In an engine having a plurality of cylinder bores arranged in one or a longitudinal direction, a plurality of bolt holes are arranged to surround the respective cylinder bores to tightly seal therearound. A gasket to be installed in this engine includes a plurality of sealing means around the cylinder bores, at which high surface pressure is formed when the gasket is tightened.
When the gasket is tightened between a cylinder head and a cylinder block by bolts, sealing means situated around the respective cylinder bores are compressed. In this respect, a bolt located in a middle portion of the engine operates to tighten two, i.e. right and left, longitudinal sides of the sealing means relative to the bolt. However, a bolt at the longitudinal end of the engine operates to tighten only one side of the sealing means, not two sides. Thus, the bolt at the longitudinal end operates to tighten the sealing means at a pressure generally twice as much as that at the middle portion of the sealing means.
The unbalanced tightening pressure causes the middle portion of the cylinder head to project upwardly. As a result, equal sealing pressure is not obtained at the sealing means.
In U.S. Pat. No. 4,834,399, a bead is formed around the entire edge portion of the gasket. However, since the bead completely surrounds the edge portion of the gasket, the bead supports all the surface pressure applied by the bolts. Namely, the bead does not support required portions.
In U.S. Pat. No. 5,199,723, a bead is formed around a water hole of a gasket, and a support bead facing a gasket edge portion is formed outside the bead. The support bead reduces vibration of the gasket at the gasket edge portion when the engine is operated.
In Switzerland Patent No. 268,267, a metal plate includes a various kinds of holes therein, around which a plurality of beads is formed to surround the same.
In the prior art patents, a various kind of beads is formed on the gasket to seal or reduce vibration of the gasket. However, the beads have not been formed around selected areas of the cylinder bores to prevent deformation of the cylinder head.
Accordingly, one object of the invention is to provide a metal gasket, which can provide by tightening bolts substantially equal surface pressure to all sealing means formed around the cylinder bores.
Another object of the invention is to provide a metal gasket as stated above, which can substantially prevent deformation of a cylinder head caused by unbalanced surface pressure on the sealing means.
A further object of the invention is to provide a metal gasket as stated above, which can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.